So what's the real deal with fatigue once treatment finishes

It's awful. I can't remember being this tired after chemo ten years ago, now I have sudden bouts of exhaustion that make me think I'm going to pass out. It's like hot flushes, one minute I'm fine, the next I'm staggering. If I lie down I can't sleep and will work myself up to the most pathetic de-energised anxiety attacks. Horrible. Between that and the muscle pain I'm not a happy camper.
And people keep telling me 'Oh, you look so well!'